Machines that are designed to produce cushion-shaped, parallelepedic-shaped, or tetrahedral-shaped packages from a continuous roll or flat web of packaging material are well known in the packaging industry. Often, such packages are used to hold single servings of consumable food products. Representative items include liquids such as fruit juice and non-carbonated beverages (which may remain liquid or be subsequently flash-frozen into solids) and semi-solids, such as sour cream or other viscous sauces.
Commonly, such packaging machines are of the “form-fill-seal” variety, in which a continuous flat web of suitable packaging material (e.g., wax- or plastic-coated paper) is formed into a vertically oriented tube-like structure by means of passing the web through one or more ring-like guides or forming collars, with a longitudinal seal formed by adhesively or thermally joining the opposed longitudinal edges of the web, often in overlapping configuration.
Once a tube of packaging material is produced, the product is introduced and it is necessary to form transverse seals to create a string of connected, filled packages. Opposed sets of heated and pressure jaws compress the tube, in spaced intervals, as the tube is moved through the machine. The string of connected packages may then be separated from one another by cutting the sealed tube segments in the region of the transverse seals.
Because the transverse seals are bisected to produce individual packages, it has been found that these transverse seals are most prone to leakage. While such leakage is less problematic when the product is frozen or very viscous (such as is the case with sour cream), the leakage rate is typically unacceptable for liquid products (such as juice or other beverages). Most often, the poor transverse seal is attributable to temperature variation from one heated jaw to another. The reason for this problem in machines of this type is that the heated jaws are constantly moving along an oval or elliptical path, which makes monitoring and adjustment of the jaw temperatures difficult.
The present disclosure addresses this deficiency in currently available equipment by providing a closed-loop electrical system for powering the heated jaws that includes equipment for monitoring the temperature of the jaw faces and for adjusting the power supplied to those jaw faces in real-time. As a result, the temperature differential among the heated jaws is considerably smaller than that of previous heated jaws, which are part of an open-loop control system.
Another issue related to existing packages with an overlapping seal is that one of the cut longitudinal edges of the packaging material is exposed to the food product. When the food products are acidic in nature, such as some juices or ketchup, or when the food products are aqueous and the packaging material includes a wickable layer (e.g., paper), the food products tend to “attack” the exposed cut edge of the packaging material. As a result, the longitudinal seals become susceptible to failure. By incorporating a “fin”-type seal in place of the traditional overlap seal, the cut edges of the packaging material remain on the outside of the formed package, and a more reliable longitudinal seal is formed. Provided herein is a subassembly for forming a fin seal on a continuous-fill packaging machine.